Download 1 We discussed function of white blood cells ,different type of white

We discussed function of white blood cells ,different type of white blood cells and it’s very
generalized picture , but you have to know the functions specific functions for each type of
white BCs (white blood cells)which one is associated with which infections, there is a certain
type of white blood cells associated with certain types of infections for example or they have
a certain functions .so for examples the lymphocytes which they are : B and T lymphocytes
are consider the main soldiers of the immune system because they are required for the final
or to complete treatment from infection, to be completely free from a certain infection we
need these two types of lymphocytes :B&T lymphocytes .now about neutrophils
macrophages we called them innate they are important but they don’t resolve the infection
completely while the B &T cells resolve the infection completely so we can’t live without
functional B & T lymphocytes .now the B cells they destroy bacteria mainly they inactivate
toxics .however T cells they have wide variety of functions may be viruses fungi transplanted
cells as well as tumor cells .you know the AIDS the problems in AIDS that there is no T cells
so as you can see without these T cells what is the results: a complete “immune deficiency
“.
Natural killer cells also they attacking wide variety invaders some of them are the tumor
cells .Now let’s talk about the functions of platelets or the thrombocytes. the physical
characteristics we are already discussed them: those are fragments of cells they came from
the megakaryocytes they contain certain factors important for coagulation their life spam is
very short: about a week (from 5 to 9 days) so this is an application of stem cell transplant
these two clinical applications for you interest for reading. so let’s go back to platelet
function hemostasis the main functions of platelet is to maintain not homeostasis but
hemostasis which means to stop bleeding .so there are certain steps or pathway there is a
pathway for this process. It has several steps:
1- The first step of doing hemostasis in our system is vascular spasms, so when there is
a wound in our skin the first thing that happens in vessels in vasculature is vascular
spasms, a vasoconstriction will happen of the blood vessels. Of course there is a
signal lead to this response, it doesn’t work automatically. So there is signaling in
cells that mediate this vasoconstrictions of the muscle layer of the vessels so this is
the first step.
2- The second step: platelets start sticking on the wound sides or edges. They start
sickness; at the beginning there is a repulsion with the wall of endothelial cells (the
inner layer of the endothelial cells) there is a kind repulsion, But when there is a
wound, the negative charges of collagen appear of the let’s say the outer wall of the
vessels so the stickiness happens. Also there is other factors, they mediate this
stickiness between platelets and the wall of the wanted wound. So they get
activated, so once they stick to the wall they get activated, and this activation leads
to rupture of these platelets and the granules get out from this platelets or lead to
exocytosis for these granules. Of course these granules contain factors, they
mediate certain things. One of these things is vasoconstrictions of the vessels wall,
another thing they increase thickness of other platelets means there would be
accumulations of more platelets and finally they constitute a plug. They form at the
end a plug.
1
3- The third step we called it blood coagulation (‫)تخثر‬, it’s different than aggregations of
platelets it’s called coagulation or clotting. back to the slide which summarize these
three steps
As you can see here this is the wound and the platelets start to stick due to the exposure of
the collagen fibres and damage of the endothelial cells. Once they stick one or two of them
stick, they cause stickiness of the others, so they form the plug. Now one of the factors is
ADP which is a result of hydrolysis of ATP (breaking), so ADP, serotonin and thromboxane A2
these are from the factors which come from platelets and they mediate either
vasoconstriction or stickiness for other platelets. So know platelet aggregation form the
plug. Until now we didn’t mention coagulation. So blood clotting is a complex pathways, it’s
not only a one pathway. It’s a complex of reactions and events that occurs after the
activation of platelets. So when ‘’ the platelet activated the blood clotting or coagulation
starts’’. So these chemical reactions involve usage of Ca +2. Calcium is a very important
cofactor for these steps, without Ca +2 clotting will never succeed. So calcium is a very
important factor. So these represent Electron microscope of these events, its very interest to
look at these events on your text book.
So let’s discuss the stages of clotting .clotting is composed of two main pathways that
combine at certain level and make one pathway.
So one pathway is called extrinsic pathway and the second pathway is called intrinsic
pathway. Both of these two pathways result in activation of an enzyme called
prothrombinase. So to worry about these pathways we need to want to see what’s the
importance of activating prothrombinase??
Prothrombinase is a pro enzyme that’s once activated it will mediate the conversion of
prothrombin into thrombin. So what is the importance of thrombin? Thrombin is the main
enzyme that we really care about because it mediates the conversion of fibrinogen into
fibrin.
Why it’s important to convert fibrinogen into fibrin? Fibrinogen is a soluble protein located
inside the plasma (when we make centrifugation we find it soluble in plasma). When
thrombin is active and available it will convert fibrinogen into fibrin. Fibrin is insoluble like
threads (‫)خيوط‬. That will form a network or a meshwork. This meshwork causes clotting or
coagulation making the blood as gel like structure (heavy gel). So this is the importance of
these two pathways, they activate prothrombinase, the enzyme that convert prothrombin
into thrombin. This we call it the common pathway (prothrombinase convert prothrombin
into thrombin) that eventually leads to formation of fibrin threads (fibrin threads then will
be stronger by certain factors, we will mention them later).
What is the two pathways that assist activation of prothrombinase?
1. Extrinsic pathway: it’s the shortcut. It’s easier, has less steps. What happen is that in
the tissue itself we call it extrinsic because the tissue that surrounds the blood vessel
secretes factors that inter the blood vessels, that’s why it’s called extrinsic pathway.
This factor is called “tissue factor” or “thromboplastin”. So what happen when this
2
tissue factor\ thromboplastin enter the vessel? With the existence of Ca+2, there will
be an activation of factor called factor number 10. Factor number 10 (we should
reach this step to make activation of prothrombinase, why?) because factor number
X will combine with another factor called factor 5 and forming a complex with
prothrombinase so prothrombinase will become active. So this step is necessary.
Note in extrinsic we directly reach this step without needing to other steps.
2. Now Intrinsic pathway: its requirement that it doesn’t need anything from tissues
(from outside the blood vessel). The requirements of this pathway is from the same
blood vessel (from the vessel wall itself) from the activated platelet. So the
requirements of this pathway is from the same blood vessel from the damaged
endothelial cells from exposed collagen in the same vessel. These damaged cells will
make activation for factor number 12, so there is an extra factor. This 12 with the
help of ca+2 and another factors come from the platelet and from the phospholipid
of platelet, will make activation of factor 10. Factor 10 and factor 5 combine with
prothrombinase making complex and make the activation of prothrombinase and
thrombin produced at the end. (Factor X=10, factor V=5). So we in this way we
reached the common pathway, so once 10 and 5 they complex with prothrombinase
the common pathway starts and produces fibrin.
Now fibrin threads firstly were loose and needs factor 13. Factor 13 make cross linking
between fibrin threads causing strengthens for this network. So you must know each factor
and its role and any factor inhibits the main pathway or common pathway or each
intrusiveness if missing factors.
So calcium as you note is needed for mostly for all the steps (only one does not needs
calcium).
Know why clot is localized? Why there is no infinite coagulation? As you see here in the
picture, these green lines, these are positive feedback loops. That means thrombin for
example make activation for factor 5 which will accelerate the production of thrombin itself.
Also thrombin make activation for platelets which also increase the production of thrombin
also. Note that there are aggravation for coagulation due to this positive feedback steps. So
does that means, that there will be infant coagulation and block the whole vessel? Is it
beneficial to block the whole vessel and stop blood there? Absolutely no, there must be
localization for the clot.
What can help the localization of clot?
1. Network. The formed meshwork makes factors more localized to this network of
fibrin. It surround them making it localized. So the concentration of these factors as
we get far from this network will be lower and not sufficient to start coagulation.
2. The second reason. There are another ongoing process, although its lower but it
starts. It is a reversible process for coagulation. Called fibrinolysis (dissolution for the
3
clotting itself). It begins slower but at the end it’ll prevent the clot from blocking the
whole vessel.
Repeating for the positive feedback loops (a student asks): in the positive feedback
loops as you note, thrombin itself is the responsible for it and its make activation for
platelets and factor 5. So it increases the velocity of the reaction because it makes
effect on the activation of the platelets itself, so increasing from pathways under
stream or downstream. Note that prothrombinase become faster increasing the
velocity of the whole common pathway.
As we said “fibrinolysis” which is opposing the thrombosis or we can say coagulation
(the responsible for coagulation is thrombin). The Fibrinolysis which is after clot
formation, it makes dissolution of the clot and not prevention of clot formation. You
should differentiate between anticoagulation (preventing the coagulation from
forming) and fibrinolysis (after the clot start, there are factors will make dissolution
for it making digestion for the clot). You should know the difference to differentiate
between anticoagulant drugs and what drugs or endogenous factors in the body
that makes fibrinolysis.
Now how fibrinolysis happens? There is an enzyme called plasmin. This enzyme
exists as proenzyme because it is not sense to a digestive enzyme to be active all the
time, so it exists as plasminogen (inactive form). This plasminogen needs to be
converted into plasmin to become activated. How the activation happened? There
are factors make the activation. One of these factors is a factor from the clotting
process itself which is factor number 12. Also there is a Factor comes from the
tissues, called tissue plasminogen activating factor, (TPA) and thrombin. Note that
there is also negative feedback loop (almost we consider it negative feedback)
because it makes mediation for other opposing pathway (she is talking about
thrombin). So at the same time another ongoing process called fibrinolysis, it starts
slightly late but it prevents thrombosis or coagulation of the whole diameter of the
blood vessel.
Know what is the function of Plasmin? Makes digestion for the fibrin threads for
fibrin network.
3. Know let us see another factor that opposes thromboxane A2. We said that
thromboxane A2 is from the factors that makes mediation for the stickiness of the
platelets. There is endogenous factor in our bodies called prostacyclin which is a
type of prostaglandins. Prostacyclin makes inhibition for thromboxane A2 so
inhibition the adhesion of the platelets. If we prevent adhesion of platelets, we
prevent activation of platelets. In this situation when we make prevention, do we
make fibrinolysis or anticoagulation? Anticoagulation. So this is another factor,
endogenous factor, comes from the body called prostacyclin, it prevents adhesion of
more platelets. (Prostacyclin prevents all the process, it is anticoagulant/ anticlotting
but plasmin makes fibrinolysis)
4
“All these are factors that prevent complete clotting of the blood vessels”
Let’s see some pharmaceutical or agents that we use as anticoagulant. What are the
anticoagulant that may be in our bodies or we may take it in form of drugs?
1- Heparin: is an endogenous agent (exists in the body) but it is also can be
manufactured and considered as a medicine. How it works? Naturally and
philologically it comes from mast cells or basophils and it mediates the inflammatory
or aggravate inflammation. Also one of the things that is do, is anticoagulation (‫)مميع‬.
How does it work? It makes activation for enzyme called antithrombin III.
Antithrombin III when activated, it makes inhibition for thrombin, and thrombin is
the most important enzyme for coagulation process. So heparin is fast acting
because it directly reach thrombin and works on.
2- Warfarin/ Coumarin: the way of mechanism of action is that it makes inhibition of
production of vitamin K. what is the importance of vitamin K? There are several
clotting factors need vitamin K to be produced in the liver. So without vitamin K we
can’t produce these factors and there will be deficiency in these factors. So as a
result for the deficiency we will get anticoagulation effect. But the action of
Warfarin is slow because it should inhibit all vitamin K in the body and so inhibition
the synthesis for all these factors, and finishing the exists factors that is already
manufactured. After all that, the effect appears. Also it is long acting, so that when
we stop using Warfarin we need long for the body to start manufacturing new
vitamin K or absorbing new vitamin K. this the difference between heparin and
Warfarin.
3- In labs they use anticoagulant when they take samples to prevent coagulation called
chelating agent (EDTA). It takes calcium, so calcium will not be available for
coagulation, and so no coagulation. We can’t give EDTA for people.
4- Aspirin: works on platelets, on platelets stickiness, so prevents adhesion of platelets.
It’s exactly similar to prostacyclin, it makes inhibition for thromboxane A2, so
prevents platelets adhesion. So it’s from the beginning prevents the adhesion of
platelets, so prevents the whole process.
Blood groups:
They divided blood into types according to the presence of certain antigens. These antigens
presented on the plasma membrane of all our cells but what we care about in blood
transfusion is red blood cells according to the present of certain antigens that are capable of
inducing immune reactions. So it has been divided into two systems;
1- ABO system. We have antigen A, antigen B (they are glycolipids), and O which refers
to no antigen, it lacks of these two antigens.
5
2- The second important system that miss transfusion leads to problems is RH (rhesus
antigen). The presence of RH antigen called RH positive and the absence RH
negative.
These are the two most important blood groups. There are many several other groups
but these are the most important.
Know we are going to take about ABO system: as I told you some people on their RBC the
have only A antigen, so their blood type is A. at the same time these people who have only
A, they have antibodies to the antigen that is not presented on their body (so they have anti
B). So in ABO system, the body produces (without exposure to the opposite blood “the
different) antibodies for the absence antigen. So we produce antibodies for antigens that are
not normally present. So a person produces B antibodies, so if we see the blood for this
person we will find RBCs with antigen A on their surfaces and we will found in serum
antibodies against B. for people who have only antigen B, we will find on their serum
antibodies against A. There are people having the two antigens, A and B on their RBCs, so
their type is AB but they don’t have antibodies for A or B because both are presented on
their RBCs, so it will not make antibodies for any of them. Type O lacks A and B antigens, so
the body produces antibodies for both A & B.
The body always produces antibodies for foreign antigens, not only for A and B but in this
case (blood) the body produces antibodies without exposing to antigens. Always the body
produces antibodies when exposure to antigens as when a microbe or virus enter our
bodies, the body starts to recognize it as foreign and starts to produce antibodies. Also in
vaccination. But in this case its unknown how our bodies recognize these foreign antigens
without exposing to it. There are many theories but it is not important to you now. So the
body produces antibodies for antigens that is not present in the body, so when exposure to
this antigen, it can starts an immune response (a huge immune response). This in ABO
system but RH is a different story. Recognize the shape of antibody (on slides). It is
composed from 5 monomers.
Know transfusion of ABO system, what we can transfuse and what we cannot? Which type
of blood it can be a universal recipient? Which type of blood can be a universal donor? O is a
universal donor. The O contains antibodies but is it important the presented antibodies in
the donor?? No, because their number is little .but what we care about is the antigen in the
recipient, is it compatible with donor or not? So when we look for who can give a body, we
should see the antigen of the recipient. For O, it can give for AB. AB has no antibodies and O
has no antigen so it is ok. Also O can transfuse for B, B has anti A but no antigen in O and at
the same time a can also takes from O because O doesn’t have antigen. That means that the
immune system for A,B, or AB will not produce an immune reaction for the presence of O.
we look at it like that, the immune system of the recipients will it make reaction against the
donor?. Know who can take from all? AB, the universal recipient. It can take from O without
problem (no antibodies), it can take from B because there are no antibodies for B, and it can
take from A because there is no antibodies for A. Now for B, it can take from the B or from
O. A can take from O or from A.
6
So this is in general. Now let us take about hereditary. Everyone takes a copy an allele from
the father and an allele from the mother for each blood group. There are three types of
alleles: A, B, and O. O allele doesn’t produce any antigen. An allele produce A antigens. B
responsible for producing B antigens. Now the person or the child takes an allele from the
father and allele from the mother. So for example if he takes A from the mother and B from
the father, the blood type will be AB. If he takes O from the father and O from the mother, it
will be O. so A and B are dominant, so if he takes A from mother and O from the father then
the A will be the dominant type of group. Also B the same, if he takes B from the mother and
O from the mother then he will be B. but O must take O from both parents. Also AB must
take A from one and B from the other parent (it is impossible for AB to take O allele).
Let’s talk about the Rh factor: The RH is another antigen, they call it Rho D factor. They first
discovered it in rhesus monkeys, so that why they call it Rhesus factor or RH (‫)العامل الريزيسي‬.
People are divided into two types, either RH positive or RH negative. The negative are less,
(rare). What matters to us in immune reaction to RH: the RH negative can transfer blood to
the positive but the positive can’t transfer and give blood to the negative, why? Because the
negative can make an immune response to the foreign antigen to him, so that’s why we
shouldn't give a negative from positive.
Now where is the problem and where is the danger happen? The danger happen when the
mom is negative RH, and then got pregnant with a positive baby (notice that in the ABO
system we didn’t talk about mum and her baby this issue doesn’t occur in the ABO system
only in the RH). In the RH system, if the mom was negative and the baby was positive
(because the father was positive RH, so the baby took the allele (gene) of the RH positive)
What happens is during the first pregnancy with an RH positive child there will be no
problems because the RBC of the baby that contain the antigen will not be transferred
through the placenta (‫)المشيمة‬to the mom so her blood and her immune system won't
recognize them, only at delivery )‫ (الوالدة‬a bleeding happens in the umbilical cord, so the
RBCs enter to the moms blood , and the immune system starts to recognize a foreign
antigen (notice in the Rh there is no antibodies originally in the body, they happen only
when the body gets exposed to the foreign antigens.
The negative RH blood doesn’t have antibodies against the positive normally, only when
transfusion happens or like this case in pregnancy of a positive child and the blood mixed).
So in the first pregnancy no problems will happen to the baby and he will be delivered. If we
suppose that no one know that the mom was negative and the baby was positive in an un
serviced area and no medical services, the baby will be born without problems and the
mothers body will take time to make antibodies against RH, in the second pregnancy if the
mother got pregnant with another RH positive baby, during the formation of the baby (the
antibodies aren’t like the ones you saw in the ABO system, they aren’t Penta polymers , they
will be able to cross the placenta) , so the antibodies that already exist in the moms body
against the Rh positive will cross the placenta and enter the baby's RBCs ,and then an
immune reaction starts and haemolysis to the RBCs ,so then a haemolytic disease happens in
the new born. This is very rare, and only happens in unserviced areas with no doctors to
7
know the blood types. Like I said, if no medical service was given, hemolysis will happen to
the RBCs and the baby will either be mentally retarded because of bleeding and the
accumulation of the hemoglobin in the brain and the nerve system will be effected or the
baby might die.
How to prevent that? From the first pregnancy, once we recognize that the mom is negative
RH and the dad is positive and there is a possible that the baby will be positive, they give the
pregnant mother before or at delivery an injection (contains antibody against RH. They call it
anti D or anti Rho D). This injection will bind with the antigens when there will be a rupture
in the umbilical cord, and it will prevent the immune response from the mother (binding to
the antigen will not trigger inflammation or immune response of the mom, and so no
memory cells will produced or antibodies from the mother herself “in other words we delete
the effect of foreign antigens”) so in second pregnancy she will not have antibodies and it
will proceed as it were first pregnancy. At the second time also the same thing, they must
also give her the injection at delivery.
Somebody asks when she would take the injection? Before 2 to 3 weeks from delivery
prediction or at delivery.
Another question: how this injection would not affect the mother? Because the amount of
the antibodies will be low referring to the mother blood and no problem because she is
already negative. It may affect the baby but it is negligible. The only effect that it prevents
the immune response for the mother at delivery when she is exposed to antigen.
Now Typing of blood, it’s very clear. How do they make blood types according to the ABO
system? We said why in the ABO system we don't care about the presence of the antibodies,
and even if the mother was pregnant with a child that has an antigen not like hers it doesn’t
matter, because the antibodies can’t cross the placenta. Now typing of blood, we bring a
sample of blood, and there is two bottles: one bottle has antibodies for A, and the second
bottle antibodies for B. We put a drop of blood and we mix with the first antiserum (anti A),
and another drop and mix with Anti B. when a reaction happen, we call it agglutination this
happens when the antigen attaches to the antibodies, makes a reaction called agglutination,
agglutination is as thrombosis (‫)تخثر‬, that makes haemolysis of RBCs and look as thrombosis.
So we call it agglutination reaction, the antigen is called agglutinogen, and the antibodies
agglutinin according to this reaction. If a reaction happen (in my experiment) that means the
blood sample has this antigen and we said he has A and If a reaction happened when mixing
with anti B ,then blood sample also has antigen B , so in this case the blood type is AB. If no
reaction happens neither with A nor with B, that means this blood type is O. If the reaction
happens only with A its type A. if only with B, then the type is B. This the classical way to find
out the blood type.
Done by: Mays ALhoubani, Noor Khanfar, Ayah Fawzi, Haneen Sabbah
Designed & reviewed by Maha Alfaloji
8